How to use multiple USB webcam in Matlab working simutaneously?

I would like to capture the live video with two USB webcams (Philips SPC 900NC), but I found that they cannot work simutaneously on my laptop. Either of the two USB webcams could work alone or work with another webcam (mounted on my laptop originally).

When I use the simulink block 'From video device', Matlab gave the error message with ' Multiple VIDEOINPUT objects cannot access the same device simultaneously.'. Then I checked the video input device with command 'imaqhwinfo', only one of the USB Philips webcam could be detected.

I would like to know that,

1. what's the reason of this situation? is it because the hardware limitation (USB bus bandwidth) or just matlab video object don't support same multiple video devices?

2. what's the solution of this? could anyone give me some suggestions?

thank you very much.

Answer 1

[Walter Roberson]

This is not a bandwidth problem, since a camera that is detected but not in active use consumes (almost) no bandwidth.

There is also no USB limitation about having multiple cameras on the same bus.

There are potential difficulties about getting acceptable frame rates when the two cameras are on the same USB bus.

I do not know why only one of the cameras would be detected. Which MATLAB version are you using?

[Jianhong Mei]

Thank you very much.

My Matlab version is R2011a, and my laptop is with Intel i3 M370, 2.4GHz, 2G RAM, win7 OS.

There are some different answers about this on internet, but I don't know which is right. is it possible that because of the USB webcam driver?

Answer 2

[Danilo Sabino]

Hi Walter, I am using 4 webcams simultaneously, however, I bought a USB HUB of 4 channels and I can not see a video preview using only 2 webcams that are plugged in the USB HUB (same USB bar).

Can you use 2 webcams in the same USB port? Because I just can use the webcams simultaneously in different port.

Thank you

[Chau Trung]

I have same problem. Can you help me ? Please.

[Walter Roberson]

User posted same question as http://www.mathworks.com/matlabcentral/answers/273344-how-to-use-multiple-usb-webcam-in-matlab